Flow Separation
Flow Separation: At sufficiently high velocities, the fluid stream detaches itself from the surface of the body.
The point of separation depends on several factors including:
Reynolds Number
Surface Roughness
Fluctuations in the Free Stream
It is usually difficult to determine where separation will occur.
Separated Region: Region between the fluid and the body.
The larger the separated region, the larger the pressure drag
Downstream velocity is reduced
Wake Region: The region of flow where the effects of the body on velocity are felt.
Pressure drag can be reduced by delaying when the separation occurs, thus reducing the pressure difference between the front and back of the body.
This can be done by streamlining the body, but this increases friction drag due to an increase in surface area.
